Hardness of Water

• Definition

It is a property of water which resist the formation of foam in soap water.

• Cause

Presence of Bivalent cations of Calcium & Magnesium.

• Disadvantages

1. Hardness cause scaling in boiler.

2. Increase soap consumption.

3. Cause incrustation of supply pipes.

4. remove color from clothes.

• Types

There is two types of hardness- 

1. Temporary Hardness or Carbonate Hardness - Hardness caused due to presence of Carbonate & Bi-Carbonates of Calcium and Magnesium [ Ca(HCO3)2,MgCo3 etc]

2. Permanent or Non-Carbonate Hardness - Hardness caused due to presence of Sulfates,Chlorides & Nitrates of Calcium and Magnesium [ MgSO4, Mg(OH)2, CaSO4, CaCl2 etc]

• Softening

The removal of hardness from water by various standard methods is known as Softening of water.

• Method's of Temporary Hardness removal

1. Boiling of  Water.

2. Addition of Lime in water.

• Methods of Permanent Hardness Removal

1. Lime Soda Process.

2. Zeolite method or Base exchange method.

3. Ion Exchange method 

• Important Notes for Competitive Exams  

1. Only Zeolite Method Can Gives us Zero Hardness.

2. Na ions do not cause hardness.
3. Some Tri-valent Cations also cause hardness like Al and Fe .

• Numerical problem